The overall objective of our research program is to determine the structure, mechanism of action, physiological function, and cellular disposition of certain kidney peptidase. Specifically, the enzymes under study are the zinc metalloenzyme, renal dipeptidase, the antidiuretic hormone-inactivating peptidase, and human urinary dipeptidase. The role of renal dipeptidase in dipeptide hydrolysis and transport within the brush border microvilli of the kidney will be investigated. Also urinary renal dipeptidase levels in urine obtained from patients with kidney tubular disorders will be determined. Urinary renal dipeptidase will be isolated, purified and characterized using techniques previously developed for the membrane bound enzyme. Isolation and characterization procedures will be employed to study the antidiuretic hormone-inactivating peptidase recently located in plasma membranes of the kidney medulla.